diff --git a/requirements.txt b/requirements.txt
index 255d57f..782ea28 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -35,7 +35,7 @@ jupyter-console==5.2.0
 jupyter-core==4.4.0
 Keras==2.1.3
 -e git://github.com/keras-rl/keras-rl.git@ea7218be9a827f515e2bc778b09b4ff9f254dfdc#egg=keras_rl
-lxml==4.1.1
+lxml==4.9.1
 Markdown==2.6.10
 MarkupSafe==1.0
 matplotlib==2.1.1